The present invention relates to electronic circuit elements having a pair of opposing electrodes such as pyroelectric elements, capacitative elements or piezoelectric elements and methods of manufacturing the same.
For example, a pyroelectric element as a electronic circuit element with opposing electrodes on each of both the surfaces of a pyroelectric substrate having predetermined electric characteristics is known. Generally, such a pyroelectric element has lead electrodes extending from the corresponding electrodes for connection to succeeding electronic circuits, as disclosed in Japanese Utility Model Application Laying Open No. Sho 58-32337.
When such a pyroelectric element is used as an infrared detector for detection of invaders, it includes a pair of pyroelectronic elements connected in series or in parallel with each other in reverse relationship in polarity (hereinafter referred to as reverse-series and reverse-parallel, respectively) so as not to respond to so-called same phase noise such as changes in room temperature or incident disturbant light, as disclosed in Japanese Patent Application Laying Open No. Sho 61-175583.
In an electronic circuit element which has opposing electrodes, that is, one on one surface of a substrate and the other on the other surface of the substrate, and lead electrodes provided on the substrate and extending from the corresponding opposing electrodes, the overlapping of the opposing electrodes and the corresponding lead electrodes which is one of the most important factors defining the element is required to be in a predetermined relationship. Otherwise, a desired given electric characteristic of the element cannot be obtained. If the overlapping varies from one manufacturing lot to another, the resulting electric characteristic of the product also varies, so that various adjustments are required when the electronic circuit element is assembled in the circuit concerned.
If, for example, a pair of pyroelectric elements is connected with each other in reverse-series or reverse-parallel relationship so as to cancel said same phase noise by outputting reverse and same phase output, the light receiving areas of both the pyroelectric elements or the area where the opposing electrodes are overlapped each other must be the same, inclusive of the corresponding lead electrodes. However, a pair of pyroelectric elements having such same area is difficult to produce.
As disclosed earlier in U.S. Pat. No. 4,983,838, the applicant made a proposal as a solution to said equality in the light receiving area in which the lead electrodes extend in the same direction in both the pyroelectric elements, such that even if the electrode pattern formation including the lead electrode on one surface of the pyroelectric substrate deviates from the other side electrode pattern, the light receiving areas of both the pyroelectric elements are the same.
However, in the element disclosed in U.S. Pat. No. 4,983,838, the lead electrodes must be extended around the opposing electrodes for wiring to thereby cause a increase in the required area of the pyroelectric member or substrate. This is one of the factors which hinder the miniaturization of pyroelectric elements or infrared detectors. Especially, when a polymer film is used as a pyroelectric substrate, a supporting base plate which is made of an alumina or plastic material is required to support the film around the periphery of the lead electrodes. Therefore, the miniaturization is further difficult as the lead electrodes are so extended around the electrode. Since the lead electrodes in the disclosed art are necessarily long, there is a high probability of disconnection at subsequent manufacturing steps. In addition, though the equality of the light receiving areas or sensitivities in a pair of pyroelectric elements can be minimized in one manufacturing lot, the sensitivity of the pyroelectric elements can still change from one manufacturing lot to another.
In a flared detector for detection of invaders and including such a pair of pyroelectric elements, the electrode dimensions are generally very small; about 1 mm wide and about 2 mm long. The distance between the opposing electrodes is between 0.8 mm and 1 mm in order to detect the move of an invader.
As be obvious from these values, generally, in a small-scaled electronic circuit element in which a pair of opposing electrodes and lead electrodes therefrom are formed on an dielectric member, a piezoelectric member, a semiconductor member or a resistant member, as well as such a pair of pyroelectric elements, the area where the opposing electrodes inclusive of the lead electrodes overlap each other or face each other with the substrate between must be considered. This is not a problem as to whether the sizes or size ratio of the electrodes and the lead electrodes is large or not, but the above disadvantages would generally occur.